1. Field of the Invention
The invention relates to a polymer, and more particularly to a phosphine-based polymer and a poly(lactic acid) material comprising the same.
2. Description of the Related Art
General polymers produced from petrifaction raw materials, for example, PET, nylon, PP and polystyrene have caused serious river and ditch blockage problems, leading to environmental pollution. Thus, displacement of such general polymers with biodegradable materials is desirable. As economies develop and living standards increase in countries like China, India and Eastern Europe, requirement for petroleum and its related products have substantially increased, resulting in rapid exhaustion of the world's petroleum inventory and rising petroleum and its related product prices. Thus, development of a biomass process utilizing natural materials, for example, soybean, corn, cane, rice and barley combined with biotechnology to produce raw materials is desirable.
Most of the products fabricated by the raw materials produced from biomass processes are biodegradable materials. Poly(lactic acid) (PLA) is prepared from a biomass process and its products possess biodegradability. Cargill Corporation has greatly invested in development of PLA. PLA's price is close to nylon and is expected to be equivalent in price to PET in the future. Currently, PLA is used mostly in commercialization of biodegradable materials or biomass materials. PLA has been widely utilized in biomedicine, agriculture, clothing, furniture, ornaments, implements for daily use and packaging materials.
Applications of PLA, however, suffer from some drawbacks, for example, brittleness, easy pyrolysis and deteriorated processability. Compared to conventional polymers, for example, PET, nylon, PE and PP, PLA's molecular weight is violently decreased during a melt process, achieving 35-60% of its molecular weight. That is, its molecular weight (Mw) ratio (Mw(after processing)/Mw(before processing)) is merely 65-40%, as reported by Bhuvanesh Gupta (Prog. Polym. Sci. 32 (2007) 455 review), such that stability and quality of products made thereof are deteriorated. The same aforementioned result also occurs for modification of the processability of textiles, plastics and thin films. Meanwhile, the decrease in molecular weight of PLA copolymers are more serious than that of PLA homopolymers.